How a session on our dyno works

A power test bench, also called a rolling road or dyno, is the reason chiptuning with us is not a matter of "load file and done". On the dyno we measure what the engine really does, instead of trusting what a table promises. This is what a session with us looks like, from driving in to the printed sheet.

Step 1: intake and health check

Before the car goes on the dyno we read the fault codes and look at the live data: boost pressure at idle and under load, fuel pressure, intake air and coolant temperature, and on diesels the load of the particulate filter. We also check the tyres and tyre pressure, because they will literally sit between the engine and the measurement.

If we find anything out of the ordinary we discuss it first. Tuning an engine with a leak in the intake or a clogged particulate filter makes no sense; the measurement would only show us the problem, not the gain.

Step 2: the baseline run

The car is strapped to the rollers, we connect the cooling and measure the standard car. This baseline run matters for two reasons. It shows whether the factory figure is correct (surprisingly often it is not, in both directions) and it is the honest reference for the result after tuning. Without a baseline every "plus 40 hp" is a guess.

Step 3: calibrate, measure, adjust

Now the software is adjusted. We raise the boost in steps, adjust injection and timing and measure again. During every run we log:

• boost pressure, requested and actual, across the whole rev range;
• exhaust gas temperature, the most important watchdog on diesels;
• intake temperature after the intercooler, the watchdog on petrol;
• lambda (mixture ratio) and, on petrol engines, knock control;
• the torque request of the gearbox on automatics.

If we see the engine hitting a limit somewhere, for example a turbo running outside its efficient range, that is where we stop. Not where the little graph looks prettiest.

This step is the difference between a generic tune and a calibration made to measure. Two cars of the same type rarely have exactly the same optimal setting: fuel, turbo wear, a different air filter or simply production spread make the difference.

Step 4: the final run and the graph

The last run produces the graph you take home: power and torque plotted against engine speed, before and after. Try it yourself, preferably with your own car: enter your number plate or look up your engine, start run 1 on the original software, then Stage 1 and GSG+, and watch how the curves stack up. Or press Play all.

This is how to read the sheet you take home:

• The torque curve should be wide and flat, not a peak that quickly falls away. A wide plateau means the car pulls in every gear.
• No dips in the curve. A dip points to a limiter fighting the new calibration, or a turbo briefly running out of breath.
• Peak power matters less than the range between roughly 1800 and 4000 rpm. That is where you drive every day; that is where the gain should be.
• Only compare runs from the same dyno on the same day. Air temperature, air pressure and tyre pressure affect every measurement. That is why we measure before and after in one session.

Step 5: test drive with data logging

A rolling road is controlled, the road is not. Wind, gradients, a fully loaded car and a hot day are conditions the dyno does not reproduce. That is why we finish with a test drive during which we log the same values as on the dyno. If everything checks out under real driving conditions, the car is ready. You take the sheets and the curves with you.

Why we do it this way

It can be done faster. Loading a file through the diagnostic port takes twenty minutes and produces the same number on paper. The difference is in what you do not see: the exhaust temperature that stays just a little too high, the knock control that intervenes now and then, the automatic reaching its torque limit. Those are the things that turn into a repair after a year. On the dyno we see them straight away.

Curious what your car does on the dyno? See under chiptuning what we expect for your engine, or book a session.